Trace analysis of phenolic compounds in water by in situacetylation coupled with purge and trap-GC/MS

Abstract

The purge-and-trap preconcentration of phenolic compounds from waters after in situ acetylation was carried out in order to quantify them by Gas Chromatography/Mass Spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Using spiked natural surface water, various parameters including purge method, derivatization reagent (acetic anhydride), pH adjuster (Na₂HPO₄), temperature and time of derivatization reaction, amount of inert salt (NaCl) added, purge time and desorb temperature have been investigated. The final optimized preconcentration conditions were as follows: 10.0 g of NaCl, 0.40 g of Na₂HPO₄ and 400 μL of acetic anhydride were added to a 35 mL sample which then was heated at 55 °C for 20 min and purged for 20 min while the trap remained at room temperature. Once the purge step was over, the trap was desorbed at 260 °C for 2 min and then baked at 270 °C for 6 min. Under these optimized conditions, the precision and detection limits for all target compounds ranged from 1.3 to 7.0% (relative standard deviation, RSD) and from 0.06 to 0.12 μg L⁻¹, and recoveries from the river water sample and wastewater sample ranged from 87.3 to 111% for all analytes. The response was found to be linear in the validated range, with the correlation coefficient (R²) better than 0.998. Finally, the method had been utilized for determination of phenolic compounds in natural surface water and wastewater samples, which suggested that it is a useful and effective method for the routine analysis of trace-level phenolic compounds in water.